Apparatus for measuring tires



Oct. 8, 1946. R. w. EVERT 8,7

I APPARATUS FOR MEASURING TIRES Filed March 21, 1945 INVENTOR. R4189 H4 fl f/if Patented Oct. 8, 1 946 APPARATUS FQR MEASURING Trans".

' 'RalphW'.' Evert, Detroit,

' states Rubber Company,

; porationof New Jersey Application M rch-2'1, 1945. Mattresses-11.}-

This invention relates to an extremely simple 1 Claim. (01. 33-178) apparatus for measuring the diameter of the tread of tires in the plane'of the wheel The larger trucks and buses nowtravelling the highways are commonly provided with dual tires;

that is two pneumatic tires for each rear wheel. It is extremely important that the two tires for the same wheel when properly inflated shall have the same diameter, for if one of the dual tires is only half an inch larger in diameter than the other, it will carry byfar the greater portion of the load upon that wheel, and as a result will be subjected to excessive wear since it carries most of the load which should be borne equally by the two tires. 7

The importance of matching dual tires as to size has been stressed heretofore, and it has been proposed to use a tire diameter caliper adapted to span the tire and measure its size, but it is very difficult for one person alone to measure the diameter of a tir with a caliper because of the length of the same required to span a large tire. Furthermorethe inner dual tire is more or less inaccessible, and in the case of buses both tires may be covered by a fender which prevents the use of such a caliper. It has also been proposed heretofore to jack up a wheel of the vehicle equipped with dual tires and determine the size of each tire on that wheel by placing a steel tape around the periphery of the tread of a tire to measure its circumference, and then similarly measure the other tire to determine how closely they are matched as to size, but this is a difficult and time consuming measuring operation.

The present invention contemplates an exa tremely simple and practical tire measuring device whereby the diameter of a tire may be determined by simply measuring the arc of a portion of the circle defined by the tire tread.

The construction and operation of the present tire measuring devic will be more fully understood from the following description when read in connection with the accompanying drawing wherein:

Fig. 1 is a perspective view of a tire measuring device such as contemplated by the .present invention. I

Fig. 2 is a, rear view of a right rear truck or bus wheel equipped with dual tires, and showing the measuring device of the present invention associated with'one of th tires; and

Fig. 3 is a side view of the wheel of Fig. 2 having the present tire measuring device associated with the outer tire.

Truck and bus tires in dual use may range in Mich; 'ass ignor to United New York, N: Y.. a corv5 size near about '26 to 58 inches "in outside diammeasuring sticketer 50f the tread. A single tire I ormeasuring'device such as contemplated by the present invention 5 4 Fig; 1 may be used to determine the diameter of tires'throughout this wide range, and such" a stick"-m'ay 'be- 'l'ess than three feet long. '--The measuring stick shown in Fig. l of the drawing may be formed throughout of either metal or wood, the latter being preferable in many cases because it will be light tohandle and inexpensive to manufacture.

The present measuring device as shown comprises a straight bar or'stick In which is provided with a curved laterally extending end or projection II having the head I2 rigidly secured thereto. The stick I!) is conveniently formed of plywood and the head [2 is hard wood slotted as shown to receive the curved end ll to which it is secured by glue and pins.

The stick I0 is provided near its other end with the graduations l3 and has slidably mounted thereupon the wooden block [4 forming a lateral projection. This block is provided with a slot l5 adapted slidably to receive the stick l0, and the outer end portion of such slot is closed by the bearing block l6 which is rigidly secured in place by glue and pins. At the bottom of the slot I5 is provided a drill hole adapted to receive the downwardly bent end of the blade spring H. The body portion of this spring bears yieldingly against one edge of the stick l0 and holds the block l6 in firm contact with the other edge of the stick. After the sliding block 14 is mounted 3 upon the stick in as shown with the spring IT in place, a protruding pin l8 is provided near the end of the stick so as to prevent the block M from slidingoff the stick. The stick may also be provided with a hole [9 adapted to receive a nail when it is desired to hang the measuring stick upon the wall when it is not in use.

Fig. 2 shows a truck or bus wheel .20 equipped with the dual tires 2| and 22. As shown the inner tire 2| is slightly larger than the outer tire 22 and as a result the inner tire is carrying the entire load as the outer tire does not contact the ground G.

In order to determine the diameter of a tire in accordance with the present invention all that is necessary is to place the measuring stick l0 against the tread of the tire so that it rests as a tangent on the tire tread as indicated by I in Fig. 3, and then it is rocked slightly in this position. until the block I! at the curved end, of the stick engages the tire tread at 2.

and"- constructed as shown in formed of a block of While the stick is in this position the block M is slid along the stick [0 until it also engages the tire tread as indicated by 3. When the gauge is so positioned it engages the tire tread at the points I, 12 and 3 which constitutes three points of an arc of the circle defined by the outer tire tread.

The length of the fixed projection at one end' of the stick I0 is indicated by a: in Fig. 3 andthe length of the sliding projection I4 is indicated by y. That is :v and y are fixed lateral distances from the stick I!) and define an arcof a predetermined depth upon the tire tread. "The length of this arc is determined by the distance between the contact points '2 and 3. The "div ameter of the tire having this measured arc is determined by reading the graduationsl.3v at the longer edge of the block l4.

It will be seen from the foregoing thatin order to use the measuring device or measuring stick'contemplated by the present invention, it

is'necessaryi to have access to only a small. por

tion of the tire circumference as will be apparent from Fig. 3, and as soon as the-measuring stick has been positioned; as shown in Fig. 3 so as to secure contact with thetire tread at the points I and 2 the block 14 is slid along the stick l0 until contact is secured at the point 3. The

size of the tire being tested may then be read Z'diameter of the tread of a tire in the plane of the. wheel, comprising a graduated bar adapted to rest with one edge tangent to the tire tread in. surface contact therewith and having a fixed :lateral projection from said edge at one end "that is provided with a tire contact point for engag the tire tread and a movable lateral projection slidably mounted on the bar near its oth'er end and having a tire contact point, the

slidably mounted projection being adapted to slide along thebar until its contact point engages the tire tread, whereupon whenwthe said edge and two points engage the tire :the diameter of the tire tread can be determined by reading thepositionof vthe slidin projection relative to said graduations.

RALPH WLEVERT. 

